When I first visited this BH in Dengkil Selangor I told the owner that the chances of any birds to fly down to the lowest floor will be closed to zero.
I gave his a few long reasoning and they were as follows:
1) The most important was the wrong positioning of the LAL.
Most BH that does well will most birds will stay at the ground floor will have its LAL is one straight line at 45 degrees flying angle. The LAL will allow the light from the entrance window to the reach the lowest ground.
The Dengkil BH designed was with this common flaw where the two LAL were somewhere in the middle of the top most floor and the second was also in the middle of the second floor.
Weir and wrongly located, I stressed to the owner.
2) I believed in the important of morning sunlight to enter a BH and guide these tenats out of the BH as early in the morning as possible.
If you wanted to build a new BH try to look at the sun path. The most important is where is the east direction.
You know that every morning the sun will rise in the east and moved to the west.
Your BH entrance hole should be facing to the east. It might not be perfect east but at least north east or south east.
Remember if you face your main entrance hole to the west, your BH will have those light a bit later as compared to facing the east.
The time to wake up and fly out to hunt for food is at a disadvantage to these birds if you face the west.
The Dengkil BH main entrance hole was facing the west.
3) The was nothing to guide those swiftlet to fly down to the lowest floor.
I have this believed that swiftlet are very stubborn and lazy. Just try to imagine of you first baby waking up in the morning to attend his tadika school.
He will usually find every excuses not to wanting to go to school because he love to sleep.
If you do not force him up he will not wakes up even for breakfast with you.
Similarly with these swiftlet.
Once they entered your BH they will usually find ways and means not to fly too far away from the entrance hole and will choose the location that will be the easiest path to fly to.
Going downstairs is not an easy thing to do unless being forced to do so.
4) There were nothing special to lure them to stay on the ground floor.
What accessories can you used to make those birds to choose the lowest floor?
For this Dengkil BH there was nothing.
No partitions, no kite tweeters, the sound volume was almost the same as the rest of the floor and so on.
By nature we know that the lowest floor of any BH will be the most conducive This is due to the fact that they are cooler and darker. The humidity of the lowest floor is generally higher.
But to get those birds downstairs you need to do more.
The above four points need to be properly understood.
If you can learn how to get them to the lowest floor, I think you will be the champion in swiftlet industry.
Please try to learn more about this subject matter and see if you mastered it before you start erecting a BH of your own.
Try not to totally dependent on your so call Bird house consultant.
He will usually , 90%, will disappoint you.